scholarly journals Caught in the act: Observation of the solvent response triggered by excited-state proton transfer in real time

2021 ◽  
Author(s):  
Claudius Hoberg ◽  
Thorsten Ockelmann ◽  
James Shee ◽  
Patrick Balzerowski ◽  
Debasish DasMahanta ◽  
...  
Keyword(s):  
Excited State ◽  
Proton Transfer ◽  
Real Time ◽  
Time Scale ◽  
Stokes Shift ◽  
Transfer Energy ◽  
Optical Pump ◽  
Excited State Proton Transfer ◽  
Electronic Response ◽  
Time Observation

Real-time observation of the solvent response following Excited State Proton Transfer (ESPT) of the photoacid HPTS into water using Optical Pump THz Probe (OPTP) spectroscopy from 0.1 ps up to 300 ps is reported. Subsequent to an instantaneous (< 0.2 ps) electronic response of the solute to photoexcitation, an oscillation with a period of 4 ps involving an intermolecular H (pyranine) - O (water) mode is observed. While for the methylated derivative, MPTS, and the deprotonated photoacid this oscillation relaxes on a time scale of 1.5 – 2 ps, for HPTS the oscillation decays more rapidly within 0.4 ps, which marks the onset of proton transfer. Energy transfer from the excited solute to the solvent takes place on a time scale of 120 ps and is proportional to the Stokes shift associated with energetic relaxation from the Franck-Condon region to the ground state of the photoexcited HPTS.

Excited-State Proton Transfer in Fluorescent Photoactive Yellow Protein Containing 7-Hydroxycoumarin

2014 ◽  
Vol 896 ◽  
pp. 85-88
Author(s):  
Dian Novitasari ◽  
Hironari Kamikubo ◽  
Yoichi Yamazaki ◽  
Mariko Yamaguchi ◽  
Mikio Kataoka
Keyword(s):  
Hydrogen Bonding ◽  
Excited State ◽  
Proton Transfer ◽  
Fluorescent Protein ◽  
Stokes Shift ◽  
Spectroscopic Studies ◽  
Photoactive Yellow Protein ◽  
Excited State Proton Transfer ◽  
Hydrogen Bonding Network ◽  
Green Fluorescent

Green fluorescent protein (GFP) has been used as an effective tool in various biological fields. The large Stokes shift resulting from an excited-state proton transfer (ESPT) is the basis for the application of GFP in such techniques as ratiometric GFP biosensors. The chromophore of GFP is known to be involved in a hydrogen-bonding network. Previous X-ray crystallographic and FTIR studies suggest that a proton wire along the hydrogen-bonding network plays a role in the ESPT. In order to examine the relationship between the ESPT and hydrogen-bonding network within proteins, we prepared an artificial fluorescent protein using a light-sensor protein, photoactive yellow protein (PYP). The native chromophore of p-coumaric acid (pCA) of PYP undergoes trans-cis isomerization after absorbing a photon, which triggers proton transfers within the hydrogen-bonding network comprised of pCA and proximal amino acid residues. Although PYP emits little fluorescence, we succeeded to reconstitute an artificial fluorescent PYP (PYP-coumarin) by substituting the pCA with its trans-lock analog 7-hydroxycoumarin. Spectroscopic studies with PYP-coumarin revealed that the chromophore takes an anionic form at neutral pH, but is protonated by lowering pH. Both the protonated and deprotonated forms of PYP-coumarin emit intense fluorescence, as compared with the native PYP. In addition, both the deprotonated and protonated forms show identical λmax values in their fluorescence spectra, indicating that ESPT occurs in the artificial fluorescent protein.

Ultrafast Excited-State Proton Transfer to the Solvent Occurs on a Hundred-Femtosecond Time-Scale

2013 ◽  
Vol 117 (16) ◽  
pp. 3405-3413 ◽  
Author(s):  
Ron Simkovitch ◽  
Naama Karton-Lifshin ◽  
Shay Shomer ◽  
Doron Shabat ◽  
Dan Huppert
Keyword(s):  
Excited State ◽  
Proton Transfer ◽  
Time Scale ◽  
Excited State Proton Transfer ◽  
Femtosecond Time Scale

Design of Large Stokes Shift Fluorescent Proteins Based on Excited State Proton Transfer of an Engineered Photobase

2021 ◽  
Vol 143 (37) ◽  
pp. 15091-15102
Author(s):  
Elizabeth M. Santos ◽  
Wei Sheng ◽  
Rahele Esmatpour Salmani ◽  
Setare Tahmasebi Nick ◽  
Alireza Ghanbarpour ◽  
...  
Keyword(s):  
Excited State ◽  
Proton Transfer ◽  
Fluorescent Proteins ◽  
Stokes Shift ◽  
Large Stokes Shift ◽  
Excited State Proton Transfer

scholarly journals Excited-State Proton Transfer in 8-Azapurines I: A Kinetic Analysis of 8-Azaxanthine Fluorescence

Molecules ◽  
2020 ◽  
Vol 25 (12) ◽  
pp. 2740
Author(s):  
Jacek Wierzchowski ◽  
Bogdan Smyk
Keyword(s):  
Excited State ◽  
Proton Transfer ◽  
Rise Time ◽  
Global Analysis ◽  
Stokes Shift ◽  
Transformation Model ◽  
Wavelength Band ◽  
Methyl Derivative ◽  
Long Wavelength ◽  
Excited State Proton Transfer

A super-continuum white laser with a half-pulse width of ~75 ps was used to observe the kinetics of a postulated excited-state proton transfer in 8-azaxanthine and its 8-methyl derivative. Both compounds exhibited dual emissions in weakly acidified alcoholic media, but only one band was present in aqueous solutions, exhibiting an abnormal Stokes shift (>12,000 cm−1). It was shown that long-wavelength emissions were delayed relative to the excitation pulse within alcoholic media. The rise time was calculated to be 0.4–0.5 ns in both methanol and deuterated methanol. This is equal to the main component of the fluorescence decay in the short-wavelength band (340 nm). Time-resolved emission spectra (TRES) indicated a two-state photo-transformation model in both compounds. Global analysis of the time dependence revealed three exponential components in each compound, one of which had an identical rise-time, with the second attributed to a long-wavelength band decay (6.4 ns for aza-xanthine and 8.3 ns for its 8-methyl derivative). The origin of the third, intermediate decay time (1.41 ns for aza-xanthine and 0.87 ns for 8-methyl-azaxanthine) is uncertain, but decay-associated spectra (DAS) containing both bands suggest the participation of a contact ion pair. These results confirm the model of phototautomerism proposed earlier, but the question of the anomalous isotope effect remains unsolved.

Sibling rivalry: intrinsic luminescence from two xanthene dye monoanions, resorufin and fluorescein, provides evidence for excited-state proton transfer in the latter

2017 ◽  
Vol 19 (36) ◽  
pp. 24440-24444 ◽  
Author(s):  
Christina Kjær ◽  
Steen Brøndsted Nielsen ◽  
Mark H. Stockett
Keyword(s):  
Excited State ◽  
Proton Transfer ◽  
Gas Phase ◽  
Emission Band ◽  
Stokes Shift ◽  
Sibling Rivalry ◽  
Core Structure ◽  
Intrinsic Luminescence ◽  
Large Stokes Shift ◽  
Excited State Proton Transfer

Excited-state proton transfer in gas-phase fluorescein monoanions results in a broad, featureless emission band and a large Stokes shift compared to resorufin, which shares the same xanthene core structure.

Excited-State Proton Transfer in syn-2-(2′-Pyridyl)pyrrole Occurs on the Nanosecond Time Scale in the Gas Phase

2011 ◽  
Vol 2 (17) ◽  
pp. 2114-2117 ◽  
Author(s):  
Philip J. Morgan ◽  
Adam J. Fleisher ◽  
Vanesa Vaquero-Vara ◽  
David W. Pratt ◽  
Randolph P. Thummel ◽  
...  
Keyword(s):  
Excited State ◽  
Proton Transfer ◽  
Gas Phase ◽  
Time Scale ◽  
Nanosecond Time Scale ◽  
Excited State Proton Transfer
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